Abstract
The coral reef ecosystem has extremely high biodiversity and are known as the “tropical rainforests in the ocean”. There are more than 6 million people engaged in coral reef fishing in the world, supporting 10% of the global fisheries catch. Coral reef fisheries are the main source of income and livelihoods for millions of people (especially in developing countries). At the same time, coral reef fisheries are also facing serious overfishing. Yongxing Island is a typical coral reef ecosystem coral island, and fishing was the only direct source of income for the original residents here. Relevant studies in recent years have shown that the fishery of Yongxing Island was overfishing. In order to better understand, protect and manage coral reef fishes in the waters adjacent to Yongxing Island of Xisha Islands, a survey was carried out on the shore catches on Yongxing Island from 2020 to 2021, and the composition of fish community structure and its changes and succession characteristics were analyzed. The results showed that: a total of 101 species of coral reef fish were found, belonging to 5 orders and 21 families. Perciformes accounted for 84.16% of the total species, and their biomass exceeded 90% of the total catch. At the family level, parrotfish have the largest number of species, reaching 21 species, with the biomass exceeds 45% of the total catch. Twenty-eight species fishes were the main fishing targets in this sea area, accounting for more than 80% of the total catch. The fishes in this sea area were overfished. First, the average weight of medium-sized and large-sized fishes in the main catch was too small, there were 9 species of large-sized fish, only 3 species had an average weight of more than 1000 g, and the average weight of other species was less than 1000 g, there were 16 species of medium-sized fish, and only 4 species had an average weight of more than 500 g. Second, most of the largest fishes in this sea area had disappeared, the largest fishes that had appeared in this sea area in the past (such as Carcharhinus limbatus, Rhizoprionodon acutus, Rhynchobatus djiddensis, Cheilinus undulatus, Plectropomus leopardus, Bolbometopon muricatum, etc.) were not found in present research. Third, a large number of carnivorous fish had disappeared. Based on present research and the characteristics of coral reef fisheries, we had compared and analyzed the family-level fish with important edible economic value. These families were Muraenidae, Sphyraenidae, Carangidae, Lethrinidae, Caesionidae, Lutjanidae, Mullidae, Haemulidae, Serranidae, Scaridae, Siganidae, Kyphosidae. There were 28 species of herbivorous fishes in this survey and 32 species in the historical survey; 49 species of carnivorous fishes in this survey and 79 species in the historical survey. Fourth, the biomass of herbivorous fish exceeds that of carnivorous fish. Early studies of coral reef ecology (i.e. primitive coral reef ecosystem) showed that coral reef fishes were mainly carnivorous, and the biomass of carnivorous was 3—4 times that of herbivorous. The coral reef fishes in this sea area had succeeded to an ecosystem dominated by herbivorous fishes. The emergence of a large number of sea urchins indicated that this coral reef ecosystem was further declining and evolving to an ecosystem dominated by sea urchins. Therefore, it is urgent to protect coral reef fishes in the waters adjacent to Yongxing Island of Xisha Islands, and it is necessary to strictly control the fishing intensity in this water.
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